JPH05194658A - Polybutadiene rubber and its composition - Google Patents

Abstract

PURPOSE:To obtain the subject polybutadiene rubber, composed of a specific polybutadiene, excellent in dynamic characteristics, abrasion resistance, tensile strength, flex crack growth resistance and impact resilience and suitable as base treads, etc., of automotive tires. CONSTITUTION:The objective polybutadiene rubber is composed of (A) 10-25wt.% portion, having 0.5-4 reduced viscosity and insoluble in boiling n-hexane and (B) 90-75wt.% portion insoluble in boiling n-hexane in which (i) the weight- average molecular weight (Mw) is 300000-800000 and (ii) the toluene solution viscosity (t-cp) and the Mooney viscosity (ML) at 100 deg.C satisfy the relation of 3ML-30<t-cp<3ML+30. Furthermore, a rubber composition excellent in runnability is obtained from >=20wt.% objective polybutadiene rubber and natural rubber and/or one or more diene-based rubbers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polybutadiene rubber and a rubber composition obtained by blending this rubber with another diene rubber or natural rubber, which is used for automobile tire members, particularly base treads, sidewalls and bead fillers. Suitable for.

[0002]

2. Description of the Related Art Recently, in the automobile industry, resource saving,
From the viewpoint of energy saving, it has been studied to further reduce the fuel consumption of passenger cars. To reduce the running fuel consumption, it is effective to reduce the weight of the automobile and reduce the running resistance. For that purpose, it is effective to reduce the rolling resistance as well as the weight of the tire itself. Therefore, various methods for reducing the weight of tires and reducing rolling resistance have been tried.

First, as one direction for reducing the weight of tires, a gauge down (reduction of thickness) of each part of the tire was studied. However, if the tread is made too thin, there is a problem that the tread is worn out in a short period of time and the tire cannot be used, and the life of the tire is shortened. On the other hand, when the thickness of the sidewall is made too thin, the rigidity of the tire decreases. Therefore, it has been found that there is a limit to weight reduction by reducing the gauge of each part of the tire.

Next, attempts were made to reduce the amount of carbon black added to the rubber of tires. Since carbon black has a large specific gravity, reducing the amount used will lead to weight reduction of the tire itself. Further, heat generation, loss modulus (E ″), and loss tangent (tan δ) of rubber can be reduced by reducing the amount of carbon black used, so that a reduction in tire rolling resistance can be expected. The rubber of No. 1 had a problem that when the amount of carbon black added was reduced, the mechanical properties, abrasion resistance, hardness, elastic modulus, etc. of the rubber deteriorated, and the performance of the tire itself also deteriorated accordingly.

Therefore, in recent years, the hardness, elasticity, wear resistance, mechanical properties, and dynamic characteristics of rubber (heat generation characteristics and tan
Improvements in δ) have been investigated. As such a rubber, an improved polybutadiene rubber in which syndiotactic-1,2-polybutadiene (SPB) is dispersed in a matrix of high cis-1,4-polybutadiene (hereinafter abbreviated as "high cis-BR") is proposed. It was done (Japanese Patent Publication Sho 49-17)
666). Since this polybutadiene rubber has a structure in which SPB is dispersed in a high cis BR matrix in a fibrous form, it has a higher hardness and elasticity than conventional rubbers such as high cis BR plain rubber. It has the characteristic of being excellent in bending crack growth. Therefore, various tire members using this improved polybutadiene have been proposed. Examples of such materials include an example used for a tread (Japanese Patent Publication No. 63-1355) and an example used for a sidewall (Japanese Patent Publication No. 55-17059).

[0006]

[Problems to be solved] However, this improved polybutadiene is also required to have a high degree of recent fuel efficiency (for example, CAFE compliance).
It could not be said to be sufficient as a material satisfying the above conditions. The present invention aims to provide a polybutadiene rubber excellent in the balance of dynamic properties and wear resistance, tensile strength, flex crack growth resistance, and impact resilience while retaining the advantages of the conventional improved polybutadiene rubber. To do.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, boiling n-hexane insoluble matter having a reduced viscosity of 0.5 to 4 ... 10 to 25% by weight (a) A weight average molecular weight (Mw) of 300,000 to 800,000, b) Boiling n-hexane-soluble component 90 satisfying the relationship that the toluene solution viscosity (t-cp) and the Mooney viscosity (ML) at 100 ° C. To 75% by weight of polybutadiene rubber.

The present invention also relates to a rubber composition obtained by blending this polybutadiene rubber with a diene synthetic rubber and / or natural rubber.

The polybutadiene rubber of the present invention will be described in detail below.

The polybutadiene rubber of the present invention has a boiling n-
It consists of hexane insoluble matter and boiling n-hexane soluble matter.

The boiling n-hexane insoluble matter is mainly composed of syndiotactic-1,2-polybutadiene and / or polybutadiene having syndiotactic-1,2-polybutadiene as a main structure. On the other hand, the component soluble in boiling n-hexane is mainly composed of high cis-1,4-polybutadiene.

The proportion of boiling n-hexane insoluble matter is 10 to 10.
It is necessary to be 25% by weight. When the proportion of the boiling n-hexane insoluble matter is less than 10% by weight, there arises a problem that the hardness, elastic modulus and breaking strength of the polybutadiene rubber are lowered. On the other hand, when the content is more than 25% by weight, the compound ML of the polybutadiene rubber becomes too high and the processability becomes difficult. The term "blend" as used herein means a polybutadiene rubber or a rubber composition obtained by blending this polybutadiene rubber with another diene rubber, with carbon black, process oil, a vulcanizing agent and the like.

The boiling n-hexane insoluble matter must have a reduced viscosity value in the range of 0.5 to 4.0 calculated from the viscosity value measured at 130 ° C. in tetralin. If the reduced viscosity is less than 0.5, the boiling n-hexane insoluble matter does not disperse in the boiling n-hexane soluble matter in a fibrous state, so that the hardness, elasticity, and flex resistance of the obtained polybutadiene rubber decrease. The problem arises. On the other hand, the reduced viscosity is 4
If it exceeds, the boiling n-hexane insoluble matter will form agglomerates in the boiling n-hexane soluble matter, which tends to cause poor dispersion, so that the processability and durability of the polybutadiene rubber are deteriorated. Occurs.

The boiling n-hexane-soluble component must have a weight average molecular weight in the range of 300,000 to 800,000, and the proportion of components having a weight average molecular weight of 50,000 or less is 3% or less (boiling n-hexane Hexane-soluble content).
The ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is preferably less than 3.0. When the weight average molecular weight is less than 300,000, there is a problem that the durability of the obtained polybutadiene rubber deteriorates. On the other hand, when the weight average molecular weight exceeds 800,000, the Mooney viscosity of the blend becomes too high, which causes a problem that processing becomes difficult. In addition, the fluidity of the compounded rubber also deteriorates.

Further, the boiling n-hexane-soluble component has its own toluene solution viscosity (t-cp) and Mooney viscosity (M
L) and 3ML-30 <t-cp <3ML + 30 must be satisfied. The toluene solution viscosity indicates the degree of entanglement of boiling n-hexane soluble components in a concentrated solution, and in a rubber having a similar molecular weight distribution, if the molecular weight is the same (that is, It is a measure of the degree of branching of the polymer chains (if the Mooney viscosity is the same). That is, in the case of the same Mooney viscosity, a low toluene solution viscosity indicates a high degree of branching, and a high toluene solution viscosity indicates a low degree of branching. In the present invention, t-cp ≦
If it is 3ML-30, the abrasion resistance and the tensile strength of the polybutadiene rubber are lowered, which is not preferable.

On the other hand, if t-cp ≧ 3ML + 30,
Formulation of polybutadiene rubber Mooney viscosity becomes too high, resulting in poor processability.

The method for producing the polybutadiene rubber of the present invention will be described below. The production method includes, for example, a two-step polymerization method.

The two-stage polymerization method is that 1,3-butadiene is first cis-1,4-polymerized into high cis-1,4-polybutadiene, and then syndiotactic-1,2 is added to the polymerization system.
2 Polymerization catalyst was added to remove the remaining 1,3-butadiene from 1,
2 Polymerize. Known 1,4-polymerization catalysts and syndiotactic-1,2-polymerization catalysts can be used. Examples of 1,4-polymerization catalysts include diethylaluminum chloride-cobalt-based catalysts, trialkylaluminum-boron trifluoride-nickel-based catalysts, diethylaluminum chloride-nickel-based catalysts, triethylaluminum-titanium tetraiodide-based catalysts, Ziegler-Natta type catalysts such as the above, and lanthanum series rare earth element type catalysts such as triethylaluminum-organic acid neodymium-Lewis acid type catalysts. Examples of syndiotactic 1,2-polymerization catalysts include soluble cobalt-organoaluminum compound-carbon disulfide-based catalysts (Japanese Patent Publication No. 47-19892) and those obtained by further adding acrylonitrile to this catalyst system (Japanese Patent Publication No. −
19893). The polymerization temperature, the polymerization solvent and the like can be appropriately set according to known methods.

The polybutadiene rubber of the present invention can also be produced by a blending method. The blending method is to polymerize high-cis 1,4-polybutadiene and syndiotactic 1,2-polybutadiene separately in advance and blend the respective polymerization solutions. other than this,
A method such as blending solid syndiotactic 1,2-polybutadiene with a polymerization solution of high-cis 1,4-polybutadiene is also possible.

The polybutadiene rubber of the present invention is a composition containing at least one rubber selected from the group consisting of high cis polybutadiene rubber, low cis polybutadiene rubber, styrene-butadiene rubber, isoprene rubber, butyl rubber, and natural rubber. Can be preferably used as a base tread or sidewall of a tire or a bead filler. However, it is desirable that this composition contains the polybutadiene rubber of the present invention in an amount of 20% by weight or more.

[0021]

EXAMPLES In the following examples and comparative examples, butadiene rubber and its composition were measured for each of the following items as follows.

Reduced viscosity of n-hexane insoluble component 25 g of polybutadiene rubber was boiled with 1000 g of n-hexane.
It was refluxed in ml and separated into boiling n-hexane insoluble matter and soluble matter. 0.2 g of the obtained boiling n-hexane-insoluble matter was dissolved in 100 ml of tetralin, and measured at a temperature of 130 ° C. with an Ubbelohde viscometer.

Measurement of weight average molecular weight of n-hexane-soluble component 25 g of polybutadiene rubber was boiled with 1,000 n-hexane.
The mixture was refluxed in ml, the boiling n-hexane insoluble matter was filtered off, and n-hexane was added.
The hexane solution was recovered. N-Hexane was removed from the obtained n-hexane solution, and the n-hexane soluble component was recovered. The recovered n-hexane-soluble component was dissolved in tetrahydrofuran, and Mw was calculated from the polystyrene reduced molecular weight using GPC. The measurement conditions are as follows. Equipment: HLC-802A type (manufactured by Toyo Soda Co., Ltd.) Column: GMH6000, 2 in parallel Eluent: Tetrahydrofuran Eluent flow rate: 1.0 ml / min Measurement temperature: Column tank ・ ・ ・ 40 ° C Detector ... 40 ℃ Sample concentration: 0.025g / 100ml Sample injection amount: 0.5ml

Micro Structure of n-Hexane-Soluble Content The boiling n-hexane-soluble content obtained by the above method was quantified by the infrared absorption spectrum method (Morero method) to determine the proportion of cis-1,4 structure.

Viscosity of n-hexane soluble component in toluene solution (T-cp) The boiling n-hexane soluble component obtained by the above method was dissolved in toluene so as to be 5% by weight, and the Cannon-Fenske viscosity was obtained. The total was measured at 25 ° C.

Mooney Viscosity of n-Hexane-Soluble Content and Formulation It was measured according to the measuring method defined in JIS-K-6300.

Hardness, impact resilience, and tensile strength of the vulcanized product were measured according to the measuring methods specified in JIS-K-6301.

For tan δ of tan δ vulcanizate, R manufactured by Rheometrics
Using SA2, temperature 70 ℃, frequency 10Hz, dynamic strain 2
% Was measured.

Exothermic characteristics Using a Goodrich flexometer, ASTM D6
23, strain 0.175 inches, load 55 pounds,
The measurement was performed at 100 ° C. for 25 minutes.

Pico Wear Measured according to the measuring method specified in ASTM D2228.

Flexural crack growth resistance J is the number of flexing cycles until a crack of 2 mm grows to 15 mm.
It was measured according to the measuring method specified in IS K6301.

[0032]

Example 1 A solution prepared by dissolving 192 g of 1,3-butadiene in 608 g of dehydrated benzene was charged into an autoclave having a volume of 2 liters whose interior was replaced with nitrogen gas, 1.9 mmol of water was further added, and the mixture was stirred for 30 minutes. Then, the temperature of this solution was raised to 50 ° C., 3.1 mmol of diethylaluminum chloride, 0.01 mmol of cobalt octoate, and 8.5 mmol of 1,5-cyclooctadiene were added and stirred to obtain 1,3-butadiene. The cis-1,4 was polymerized. Three
After 0 minutes, 3.6 mmol of triethylaluminum as a syndiotactic 1,2 polymerization catalyst, 0.2 mmol of carbon disulfide, and 0.12 of cobalt octoate were added to the polymerization solution.
0 mmol was added, the temperature was adjusted to 50 ° C., and the mixture was stirred for 30 minutes to polymerize the remaining 1,3-butadiene by syndiotactic 1,2. After completion of the polymerization, add 2,4-
A solution of 0.5 g of tert-butyl-p-cresol dissolved in a methanol-benzene mixed solvent (50:50) was added to terminate the polymerization reaction. After stopping the polymerization reaction,
The polymerization solution was treated according to a conventional method to recover the polybutadiene rubber. The obtained polybutadiene rubber had a Mooney viscosity of 65 (ML _{1 + 4} , 100 ° C.), a boiling n-hexane insoluble content of 12.1% by weight, and a boiling n-hexane soluble content of 87. It was 9% by weight. The boiling n-hexane insoluble matter had a reduced viscosity of 2.1. The boiling n-hexane soluble component has a Mooney viscosity of 50 (ML _{1 + 4} , 100
℃), toluene solution viscosity 150, weight average molecular weight 6
It was 30,000, and the ratio of cis-1,4 structure was 96.9%. The above results for this polybutadiene rubber are shown in Table 1. According to the formulation table of Table 2, carbon black, process oil, sulfur and the like were blended with this polybutadiene rubber, and the mixture was pressed at 150 ° C. for 30 minutes and vulcanized to prepare blends (Samples 1 and 2). Samples 1 and 2 were measured for hardness, 300% stress, tensile strength, impact resilience, heat generation and the like. The measurement results are shown in Table 3. Furthermore, Table 4,
Formulation for sidewall according to the formulation table of 6 and 8,
A base tread formulation and a bead filler formulation were prepared. For these formulations, hardness, 300%
The stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Tables 5, 7, and 9.

[0033]

Example 2 Water was added at 1.8 mmo in cis-1,4 polymerization.
Example 1 except that the amount of 1,1,5-cyclooctadiene was 10.5 mmol and the amount of cobalt octoate was 0.20 mmol in the syndiotactic 1.2 polymerization.
Two-stage polymerization was carried out in the same manner as above to obtain a polybutadiene rubber. Table 1 shows the results of measurement of the ratio of the n-hexane insoluble matter, the Mooney viscosity and the toluene solution viscosity of the n-hexane soluble matter of this polybutadiene rubber. Carbon black, process oil, sulfur, etc. were blended with this polybutadiene rubber according to the blending table in Table 2, and the blended amount was 30 ° C. at 150 ° C.
Samples 3 and 4 were prepared by pressing for 1 minute and vulcanizing.
With respect to Samples 3 and 4, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Table 3. Further, according to the formulation tables of Tables 4, 6 and 7, a sidewall formulation and a base tread formulation were prepared. With respect to these blends, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Tables 5, 7, and 9.

[0034]

Example 3 In cis-1,4 polymerization, the amount of 1,5-cyclooctadiene was set to 10.0 mmol, in syndiotactic 1.2 polymerization, the amount of triethylaluminum was 3.9 mmol, and the amount of cobalt octoate was changed. 0.20 mmol
Except that the two-stage polymerization was carried out in the same manner as in Example 1,
A polybutadiene rubber was obtained. Table 1 shows the results of measurement of the ratio of the n-hexane insoluble matter, the Mooney viscosity and the toluene solution viscosity of the n-hexane soluble matter of this polybutadiene rubber. Then, according to the composition table of Table 2, carbon black, process oil,
Sample 5 was prepared by blending sulfur and the like, pressing at 150 ° C. for 30 minutes and vulcanizing. For sample 5, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Table 3. In addition, Tables 4, 6, and 8
According to the formulation table of 1., a sidewall formulation and a base tread formulation were prepared. For these formulations,
Hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Tables 5, 7, and 9.

[0035]

Example 4 The amount of water was 1.9 in cis-1,4 polymerization.
5 mmol and the amount of triethylaluminum in the syndiotactic 1.2 polymerization was 3.5 mmol.
Two-stage polymerization was carried out in the same manner as in Example 1 to obtain a polybutadiene rubber. Table 1 shows the results of measurement of the ratio of the n-hexane insoluble matter, the Mooney viscosity and the toluene solution viscosity of the n-hexane soluble matter of this polybutadiene rubber.
Then, carbon black, process oil, sulfur and the like were blended with the polybutadiene rubber according to the blending table of Table 2, and the blended rubber was pressed at 150 ° C. for 30 minutes and vulcanized to prepare Sample 6. For sample 6, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Table 3. In addition, Tables 4, 6, and 8
According to the formulation table of 1., a sidewall formulation and a base tread formulation were prepared. For these formulations,
Hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Tables 5, 7, and 9.

[0036]

Comparative Example 1 Polybutadiene rubber was obtained by carrying out two-step polymerization in the same manner as in Example 1 except that the amount of cobalt octoate was 0.08 mmol in cis-1,4 polymerization.
The polybutadiene rubber obtained has a Mooney viscosity of 60.
(ML _{1 + 4} , 100 ° C.), the boiling n-hexane insoluble content was 7.8 wt%, and the boiling n-hexane soluble content was 92.2 wt%. The boiling n-hexane insoluble matter had a reduced viscosity of 2.1. The boiling n-hexane soluble component had a Mooney viscosity of 48 (ML _{1 + 4} , 100 ° C.), a toluene solution viscosity of 132, a weight average molecular weight of 520,000, and a cis-1,4 structure ratio of 96.7%. Met. The above results for this polybutadiene rubber are shown in Table 1. According to the blending table in Table 2, carbon black, process oil, sulfur, etc. were blended with this polybutadiene rubber to give 150
Sample 7 was prepared by pressing at 30 ° C. for 30 minutes and vulcanizing. With respect to Sample 7, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Table 3. Further, according to the formulations of Tables 4, 6 and 8, a formulation for sidewall and a formulation for base tread were prepared. With respect to these blends, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Tables 5, 7, and 9.

[0037]

[Comparative Example 2] 1.7 mmo of water in cis-1,4 polymerization
Two-step polymerization was carried out in the same manner as in Example 2 except that the amounts of l and cyclooctadiene were changed to 10.0 mmol to obtain polybutadiene rubber. The polybutadiene rubber obtained had a Mooney viscosity of 62 (ML _{1 + 4} , 100 ° C.) and a boiling n-hexane insoluble content of 18.3% by weight. The Mooney viscosity of the n-hexane soluble component was 41, and the weight average molecular weight was 500,000. The results are shown in Table 1. Then
Carbon black, process oil, sulfur, etc. were blended with this polybutadiene rubber according to the blending table in Table 2 to obtain 150
Sample 8 was prepared by pressing at 30 ° C. for 30 minutes and vulcanizing. With respect to Sample 8, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Table 3. Further, according to the formulations of Tables 4, 6 and 8, a formulation for sidewall and a formulation for base tread were prepared. With respect to these blends, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Tables 5, 7, and 9.

[0038]

Comparative Example 3 The amount of water was 1.7 in cis-1,4 polymerization.
A polybutadiene rubber was obtained in the same manner as in Example 2 except that the amount was 5 mmol and the amount of diethylaluminum chloride was 3.3 mmol. The polybutadiene rubber obtained had a Mooney viscosity of 62 (ML _{1 + 4} , 100 ° C.) and a boiling n-hexane insoluble content of 18.3% by weight. n-
The Mooney viscosity of the hexane-soluble component was 38, and the weight average molecular weight was 480,000. The results are shown in Table 1. Then, carbon black, process oil, sulfur, etc. are blended with this polybutadiene rubber according to the blending table in Table 2, and 1
Sample 9 was prepared by pressing at 50 ° C. for 30 minutes and vulcanizing. For sample 9, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Table 3. Further, according to the formulations of Tables 4, 6 and 8, a formulation for sidewall and a formulation for base tread were prepared. With respect to these blends, hardness, 300% stress, tensile strength, impact resilience, heat generation, etc. were measured. The measurement results are shown in Tables 5, 7, and 9.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

[Table 6]

[0045]

[Table 7]

[0046]

[Table 8]

[0047]

[Table 9]

[0048]

The polybutadiene and the rubber composition of the present invention retain the advantages of the conventional improved polybutadiene rubber as they are, and have an excellent balance of dynamic properties and wear resistance, tensile strength, flex resistance and impact resilience. ing.

Claims (2)

[Claims] 1. A boiling n-hexane insoluble matter having a reduced viscosity of 0.5 to 4 ... 10 to 25% by weight (a) a weight average molecular weight (Mw) of 300,000 to 800,000, and (b) a toluene solution The viscosity (t-cp) and the Mooney viscosity (ML) at 100 ° C. are 3ML-30 <t-c.
A polybutadiene rubber having a boiling n-hexane soluble content of 90 to 75% by weight, which satisfies the relationship of p <3ML + 30. 2. (a) Polybutadiene rubber according to claim 1, 20% by weight or more (b) Natural rubber, and / or at least one type of diene synthetic rubber. ..Rubber composition that is the balance.